In general, tensions of a plurality of independent suspended wire ropes become unbalanced while an elevator is reciprocated by the wire ropes.
The unbalance of the tensions is periodically managed, but since the tensions are changed in real time according to a temperature of the field where the elevator is installed and the number of operations of the elevator even if the tensions are periodically checked and managed, the unbalance remains until the next check.
The unbalance of the tensions causes eccentric wear of the pulleys and a difference in number it of the pulleys, which causes a difference in feeding distances of the wire ropes. Thus, the wire ropes are slipped during driving of the pulleys, causing longitudinal and transverse vibrations, and directly causing vibrations to the elevator.
Accordingly, this causes a subsidiary breakdown of the elevator, shortening a life span and deteriorating a riding comfort of the elevator.